The present invention relates generally to the field of etching and cleaning. Specifically, the present invention relates to methods and compositions for application of etchers and cleaners having a color-changing component for control of the degree of etching.
Etchers are compounds used typically to remove a portion of a surface. Acid etchers are widely used in the coatings industry to etch surfaces, such as concrete floors, before applying a coating. The etching process cleans the surface and yields a surface profile suitable for obtaining a good application of the coating, as well as promoting better adhesion to the substrate. Most etchers are made of organic or inorganic acids or salts. As such, most current etchers are colorless or contain very light color.
Current form of etchers have several general problems. First, a very common phenomenon is that the surface cannot be uniformly etched if the thickness of the etching product is not applied uniformly. For example, a light application of the etching product on the area to be etched will have degraded performance compared to a similar area with a much heavier application. With colorless etchers, it is very difficult for a user to determine if a uniform application of the etcher has been made. Second, it is very difficult to judge when the etcher has lost all of its etching capability. Etchers react with the surface, such as concrete, which results in a gradual neutralization of the acid. Thus, at some point the etcher will become essentially neutral, losing its etching ability; but a user has no easy way to determine when that has occurred. However, it is often desirable to remove this residual etcher rather than to simply leave it on the surface Third, it is difficult to determine when it is the proper time for the user to rinse the etched area if there is no clear distinction between areas that have been properly etched as compared to those that still require time for the product to etch fully. This is particularly important in more precise etching applications where a certain amount of etcher is to be applied for a certain time.
Thus, there is a need for an etching composition and methods for using the same that provides a color-changing mechanism which provides a sensitive indicator of the proper level of completion of a desired process.